The importance of phytate in phosphorus (P) cycling in soil and manure has long been recognized. Phytate is a storage compound in seeds that cannot be fully digested by many animal species, resulting in the accumulation of phytate in manures. It can enter the soil either directly from plants, or from application of manures. In this chapter we will discuss the abiotic and biotic factors that control the cycling and bioavailability of phytate in soil and manure. An understanding of these processes is key to enhancing the availability of P to plants and animals, minimizing the losses of P from soil to water, and sustainably managing the use of P in agricultural systems.